This invention relates to phase equalization circuits and more particularly to improved arrangements for generating error control signals for use in automatic phase equalizers.
In frequency division multiplexers and communications systems having a plurality of signals or signal components, it is frequently necessary for proper system operation to maintain phase equality between the signals or signal components. Because the values of electrical components in such systems drift with time and temperature changes, it is necessary to make adjustments in order to maintain phase equality between signals.
Although the circuit of the invention is applicable in any environment where phase equality between two signals or signal components must be maintained, it is particularly well suited for a LIND (linear amplification using nonlinear devices) amplifier because the circuit selectively equalizes only phase variations associated with drift in value of electrical devices with time and temperature. The circuit of the invention does not affect phase fluctuations of signal components due to desired modulation. In a LIND amplifier, an original bandpass signal to be amplified is separated into two components. These components are separately amplified by nonlinear devices and the amplified resultants recombined to produce a replica of the original bandpass signal. Phase equality between the amplified signal components must be maintained for the LIND amplifier to function properly.
Simple means for detecting and correcting phase differences due only to electrical component drift while leaving desired phase modulation terms unchanged are not available in the prior art. Prior art phase equalizing devices such as phase-locked loops are not suited for use in conjunction with a LIND amplifier because phase-locked loops equalize all phase fluctuations rather than selectively equalize only those fluctuations associated with electrical component drift as required in conjunction with a LIND amplifier.